Data Annotation.
The collected videos are annotated on two levels: the MG categories, and the emotion categories. The emotions are annotated on video level, i.e., one emotion label for each press conference video. We consider two emotion categories: positive, i.e., corresponding to the winning case, and negative, i.e., corresponding to the losing cases. Then we search through the videos to spot and exert all MG instances (clips) and assign MG category labels for them. The work of MG annotation was very difficult and time consuming, and we took three measures as follows to ensure the quality of annotation.
1) Clarify the scope and categories of MGs.
According to reference psychological studies [1]}, [2]}, [3]}, MGs could be clusters as five major groups according to the motions' locations and functions, i.e., “Head”, “Body”, “Hand”, “Body-Hand”, and “Head-Hand”, and each major group contains multiple fine-categories of MGs. The iMiGUE covers altogether 31 categories of MGs plus one extra category of non-MGs, i.e., illustrative gestures (see Fig. REF  (a) for details).
2) Multiple labelers and training for labeling.
We have five persons working together on MG annotation for two reasons: the first is to speed up the process, and the second is to reduce personal bias for more reliable annotation. Before the actual annotation, all five were trained to unify their criteria for MG annotation. First, they went through the descriptions and sample figure or video of the 32 categories of iMiGUE to get understanding of the characteristics of MGs, and primarily rules of instance durations (the starting and ending points) were also discussed. Then, they went through three rounds of labeling exercises, i.e., in each exercise, every labeler first labeled two sample clips separately and then compared their labels together, different opinions were carefully discussed until agreements were reached by all annotators.
3) Cross check for reliable annotations.
The task of annotating all video clips was divided for five persons to ensure that every clip has two labelers. After all five labelers finished labeling, a cross check of their annotations were carried out following the Eq.  REF
\(\mathcal {R} = \frac{2\times MG(L_{i},L_{j})}{\# All\_MG},\) 
